Process for making half-tone enlargements.



No 820,053. Q PATENTED MAY 8, 1906.

V. LAMB.

PROCESS FOR MAKING HALF TONE ENLARGEMENTS.

' APPLICATION FILED DEC. 23. 1904.

$11 man ['01 UNIE s VIRGIL LAMB, OF

AES

ATENT FFIQE.

CINCINNATI, OHIO.

Specification of Letters Patent.

Patented May 8, 1906.

Application filed December 23, 1904. Serial No. 238,044.

To all whom, it may concern.-

Be it known that I, VIRGIL LAMB, a citizen of the United States,residing at Cincinnati, in the county of Hamilton and State of Ohio,have invented certain new and useful Improvements in Processes for MakinHalf- Tone Enlargements, of which the f0 lowing is a specification.

My invention relates to a process for creating a half-tone ima edirectly upon a sensitized plate, prefera ly metal, from a nonhalf-tonedimage.

The invention has its most practical realization in enlarging pictures,though the size of the created image is merely an incident depending uon the distance of the metal plate om the o jective lens.

The figure re resents a diagrammatic elevation of a speci c arran ementof the apparatus which may be emp oyed to carry out my process.

A represents an ordinary search-light tube.

B represents the parabola reflector.

C D represent the carbons of the arc-light.

E re resents a water-tank having glass sides (1 and placed in front ofthe reflected li ht.

F re resents a condensing-lens. Preferably t e image G is the ordinaryphotographic negat ve plate, though the process will be operative with apositive plate. By the ordinary plate I mean a late which has not beensubjected to the hal -tone process. H represents an objective lens. Iplace between the two lenses the said plate and at a suitable distancefrom the objective lens the metal plate. It will be understood that thisprocess so far described projects an image larger than the negative u onthe plate. I place a half-tone screen J 0 the size of the plate Iimmediately adjacent to the plate, which distance may be slightlyvaried,

according to the quality of the picture desired. This metal plate I has1ts surface coated with an emulsion which becomes hardened when exposedto light, such as a mixture of glue and bichromate of ammonium. Thelight-rays which are permitted to pass through the meshe sof this screenform hardened s ots on the sensitized surface, varying in size with thedifferent degrees of li ht passin through the small negative ate. At t esame time the light-rays deected around the opaque meshes of the screenby continued exposure s read these spots over an increasing area 0 theplate,

and through the meshes of the screen.

thereby creating the ima e in-thickly-dotted hardened-s ots, frequentIyuniting into solid masses. hen the exposure has been sufiicient toproduce the difierent-sized dots, the plate may be washed with water,which will dissolve out the unfixed portions of the sensitized surfaceof the late, thereby leavin the image created on t eplate in a thick anmatted nebula of hard spots.

In the ordinary half-tone process the enlarged image is projectedthrough a half-tone screen upon a sensitized glass late, therebycreating'the image upon the g ass in a series of colored spots ofvarying size and shade corresponding to the res ective light-raystransmitted throughthe p otographic p llalte e image thus formed on theglass plate is a halftone, which must be transferred to the ordinaryzinc plate. This is accomplished by a separate transferrin process. Myprocess projects the non-hal -tone image of an ordinary photographic.plate through ascreen and upon a metal plate, thereby creating thehalf-tone picture directly on the sensitized zinc plate in one singleand comparatively short operation.

The prior half-tone processes in common use are more ex ensive, not onlybecause of the greater lengt v of time and labor required, but also byreason of a greater consumption of material. It is particularly exensive in enlarging work, because the ha f-tone is formed on a lar e andex ensive glass plate. It is impractica to hand e a very large lassplate, and so this half-toning process has imitations in size. Anotherconventional halftoning process is to form the half-tone icture on aglass plate in one process and t en project an enlarged image thereofupon a senis not only a two-step process, but an inferior quality of imae is created, for the reason that the distance etween the dots formingthe image is increased by the enlar ing process. It should be understoodthat tile quality of the enlarged image ona half-tone plate is improvedin direct ratio with the density an size of the dots. In my process notonly are the dots thickly inters ersed, but the spreading of these dots,as a ove ex lained, makes a very superior image. It wi be understoodthat after my process the zinc plate is ready for the acid-bath, thesubsequent treatment, of the plate being of the ordinary character.

sitized metal plate in a second process. This IIO Having described myinvention, 1 claimplate, and finally treating. such plate to pro- 10 Theherein-described process of producing duce thereon a dprinting surface,substanan enlarged half-tone printing-plate from an tially as describeordinary photograph which consists in pro- In testimony whereof I havehereunto set 5 jecting a photograph through a magnifymgmy hand.

lens upon a metal plate, the surface of which H VIRGIL LAMB.

has been coated with an emulsion adapted to Witnesses:

harden u on exposure to the light, interpos- OLIVER B. KAISER,

ing a hal -tone screen between the lens and, g LEO ODONNELL.

